Can't ping localhost when not connected to network

**DanDare** · July 8th, 2010

Hi there,

As the title says, I'm having trouble pinging localhost, specifically, pinging localhost when I'm not connected to a network.

When I try it keeps telling me the operation is not permitted:

Code:

matt@mubuntu:~$ ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted

But if I connect to the network, start pinging then disconnect it continues pinging.

Google seems to think it could be something to do with my iptables setup:

Code:

matt@mubuntu:~$ sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            ctstate RELATED,ESTABLISHED 

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Or my routes:

When connected to network

Code:

matt@mubuntu:~$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     1      0        0 eth1
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 eth1
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth1

When not connected to network

Code:

matt@mubuntu:~$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo

But as far as I can tell there isn't anything in there which would stop me connecting to the localhost (I also can't connect to my local apache instance when offline)...

I'm at a loss as to what to do, does anyone have any ideas as to what I'm doing wrong.

(It's worth mentioning that a couple of weeks ago I had the pc setup to share it's internet connection with a laptop, ala this guide, however I've since disabled the iptables rules and disabled ip forwarding.)

**DanDare** · July 8th, 2010

Ok, turning off iptables got it working but I have no idea why...

Is there a reason behind it blocking access to localhost only when disconnected from the network and is there some way to fix this?

**Iowan** · July 9th, 2010

Apparently, I'm already off-base, but...
What is in your /etc/hosts file?

**DanDare** · July 9th, 2010

Hi Iowan,

Not quite sure how but since iptables was disabled everything's been working fine, even when iptables was re-enabled.

It seems very odd...

Thanks for your help anyway!

**Iowan** · July 9th, 2010

Odd, indeed...
Give it a couple of days to see if it stays working before marking the thread [SOLVED].

**laugh** · October 31st, 2011

i have the same problem but it didn't get resolved by switching off iptables.

as soon as i disconnect from internet (with gui networkmanager), both "ping localhost" and "ping 127.0.0.1" return:

ping: sendmsg: Operation not permitted

i switched off iptables, "iptables -L" gives:

Code:

Chain INPUT (policy ACCEPT)

target prot opt source destination

Chain FORWARD (policy ACCEPT)

target prot opt source destination

Chain OUTPUT (policy ACCEPT)

target prot opt source destination

/etc/hosts contents:

Code:

127.0.0.1	localhost
127.0.0.1	glocalhost
127.0.1.1	ubuntu.ubuntu-domain	ubuntu

route -n with network on

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     2      0        0 eth1
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 eth1
0.0.0.0         192.168.1.254   0.0.0.0         UG    0      0        0 eth1

route -n with network off is empty:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

**laugh** · October 31st, 2011

oh, right, i don't have loopback interface

it's described in /etc/network/interfaces though

Code:

auto lo
iface lo inet loopback

auto eth1
iface eth1 inet dhcp

what should i change to turn it on?

**laugh** · November 1st, 2011

ps.

Code:

sudo ifconfig lo up

doesn't change anything

**laugh** · November 5th, 2011

help anyone?

i am a web developer and live in country where electricity often goes off, so i cannot develop when i don't have wireless

because localhost is inaccessible and all my local servers stop being accessible(i have apache and nginx)

**laugh** · November 5th, 2011

help anyone?
it's bigger than it seems - i am a web developer and live in country where electricity often goes off, so currently i cannot develop when i don't have wireless

because localhost is inaccessible and all my local servers stop being accessible(i have apache and nginx and rack)